The Royal Gramma is not considered an aggressive species, but their look-alike, the Royal Dottyback, or Dottyback, is. You can tell the difference between these two species by looking at them. Royal Grammas have a gradual color shift from their heads to their tails while the Dottyback have a clear line that separates their colors.

The royal dottyback is very similar in looks to the royal gramma, which sports almost exactly the same purple-yellow bicolor pattern. If you’re not sure, just have a look at the dorsal fin. If the fish lacks an obvious black dot, then you’re dealing with the dottyback, not the gramma.